This invention relates to a process of preparing polyolefins, and more particularly to the polymerization or copolymerization of olefins using novel catalysts.
Heretofore, there have been proposed a great many catalysts useful for the production of polyolefins. Among such known catalysts are the ones which are obtained by contacting transition metal compounds such as titanium and/or vanadium with organometal compounds of Groups I-IV metals of the Periodic Table. An improvement in this type of catalyst is also known which comprises a transition metal compound such as for example titanium tetrachloride supported on an inorganic solid carrier such as magnesium hydroxychloride, magnesium halide, magnesium hydroxide, magnesium oxide or the like and subsequently activated by an organometal compound. Such supported catalysts are normally very active and in most cases active enough to dispense with the step of catalyst removal which is rather complicated in the process of polyolefin preparation. For this reason, the recent trend in the art has been directed to the use of magnesium and various other metallic compound carriers for catalyst components.
However, while solid carriers of the type consisting of magnesium hydroxychloride and magnesium halide contribute to increased catalytic activity, they have the drawback that halogen content is relatively high in the polyolefin which is obtained by a process dispensing with the step of catalyst removal. Whereas, another type of carrier consisting of magnesium oxide and magnesium hydroxide is advantageous in respect of the halogen content, but has much to be desired for catalytic activity. It is known to improve the activity of magnesium oxide or magnesium hydroxide supported catalysts by halogenating these magnesium compounds. This however still involves the problem of halogen residues in polymerized products.